Rotating device

ABSTRACT

A rotating device includes a fixed body having a base and a shaft, a hub, and a rotating body having a rotating-body-side encircling member fixed to the hub and encircling the shaft. A lubricant is present between the fixed body and the rotating body. The rotating-body-side encircling member and the shaft are each formed with a radial dynamic pressure generating groove. The fixed body includes a base-side encircling member having a disk part encircling the base-side portion of the shaft and a cylinder part encircling the rotating-body-side encircling member. The base-side encircling member has the disk part fixed to the shaft by interference fitting, and has the cylinder part fixed to the base. An air-liquid interface is located in a gap in the radial direction between the inner periphery of the cylinder part and the outer periphery of the rotating-body-side encircling member.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Divisional of U.S. application Ser. No. 13/316,798, filed Dec.12, 2011, which claims the priorities based on Japanese PatentApplication No. 2011-006827 filed on Jan. 17, 2011, Japanese PatentApplication No. 2011-121322 filed on May 31, 2011, and Japanese PatentApplication No. 2011-121981 filed on May 31, 2011, the entire contentsof all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotating device that has a shaftfixed to a fixed body.

2. Description of the Related Art

Disk drive devices like a hard disk drive are well developed forreduction in size and increase of a volume, and are built in variouselectronic devices. In particular, such disk drive devices are nowadaysbuilt in portable electronic devices, such as a laptop computer and aportable music player. In comparison with disk drive devices built in aso-called stationary electronic device like a desktop PC (PersonalComputer), resistances against shock and vibration are necessary fordisk drive devices built in such portable electronic devices so as towithstand against a shock due to a falling and a vibration during acarriage.

For example, JP 2009-162246 A and JP 2010-127448 A disclose motorshaving a shaft fixed to a base plate and having a bearing that employs afluid dynamic bearing mechanism.

According to the conventional shaft-fixed motors disclosed in JP2009-162246 A and JP 2010-127448 A, a dynamic pressure generator isformed in the direction of a rotation axis R so as to be held betweentwo tapered seals. According to this structure, however, when thethickness of a motor is restricted, it is necessary to reduce thedimension of the dynamic pressure generator in the direction of therotation axis R. This reduces the rigidity of a bearing and harms theresistances of the motor against shock and vibration.

Alternatively, it is necessary to reduce the dimension of the taperedseal in the direction of the rotation axis R. In this case, in order tomaintain the lubricant retaining amount by the tapered seal, if a spacein a radial direction is increased, capillary force becomes poor. Whenthe capillary force by the tapered seal becomes poor, the lubricantoften leaks out.

Such a technical issue arises in the cases of not only the motors butalso other kinds of rotating devices, in particular, a rotating devicehaving a shaft fixed to a fixed body and employing a fluid dynamicbearing.

The present invention has been made in view of such a circumstance, andit is an object of the present invention to provide a rotating devicewhich allows improvement of the rigidity of a bearing or which reducesthe leak-out of a lubricant.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a rotating device. Therotating device includes: a fixed body including a base and a shaftfixed to the base; a rotating body including a rotating-body-sideencircling member that encircles the shaft and a hub which is fixed tothe rotating-body-side encircling member and on which a recording diskis to be mounted; a lubricant continuously present between the rotatingbody and the fixed body from one air-liquid interface to an otherair-liquid interface; a first dynamic pressure generating groove formedin either one of an inner periphery of the rotating-body-side encirclingmember and an outer periphery of the shaft; and a second dynamicpressure generating groove formed in either one of the inner peripheryof the rotating-body-side encircling member and the outer periphery ofthe shaft so as to be distant from the first dynamic pressure generatinggroove in an axial direction, a distance between the two air-liquidinterfaces of the lubricant in the axial direction being shorter than adistance from a portion of the first dynamic pressure generating grooveopposite to the second dynamic pressure generating groove to a portionof the second dynamic pressure generating groove opposite to the firstdynamic pressure generating groove.

A second aspect of the present invention provides a rotating device. Therotating device includes: a fixed body including a base and a shaftfixed to the base; a rotating body including a hub on which a recordingdisk is to be mounted, and a rotating-body-side encircling member whichis fixed to a hub opening provided in the hub and which encircles theshaft; a lubricant continuously present between the fixed body and therotating body, the lubricant including at least a first air-liquidinterface and a second air-liquid interface; and a radial dynamicpressure generating groove which is formed in either one of surfaces ofthe rotating-body-side encircling member and the shaft where thelubricant contacts, and which generates radial dynamic pressure, thefixed body further including a base-side encircling member comprising adisk part that encircles a base-side portion of the shaft and a cylinderpart that encircles the rotating-body-side encircling member, and thefirst air-liquid interface being located in a gap in a radial directionbetween an inner periphery of the cylinder part and an outer peripheryof the rotating-body-side encircling member.

A third aspect of the present invention provides a rotating device. Therotating device includes: a fixed body including a base and a shaftfixed to the base; a rotating body including a hub on which a recordingdisk is to be mounted and a rotating-body-side encircling member whichis fixed to a hub opening provided in the hub and which encircles theshaft; a lubricant continuously present between the fixed body and therotating body; and a radial dynamic pressure generating groove which isformed in either one of surfaces of the rotating-body-side encirclingmember and the shaft where the lubricant contacts, and which generatesradial dynamic pressure, the fixed body further including a base-sideencircling member comprising a disk part that encircles a base-sideportion of the shaft and a cylinder part that encircles therotating-body-side encircling member, and the base-side encirclingmember being integrally formed with the shaft, and having the cylinderpart bonded and fixed to a through hole provided in the base.

Any combination of the above-explained structural elements andreplacement of the structural element and expression of the presentinvention between a method, a device, and a system are also effective asan embodiment of the present invention.

According to the present invention, the rigidity of a bearing can beimproved or the leak-out of a lubricant can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram showing a rotating device according to a firstembodiment of the present invention;

FIG. 1B is a diagram showing the rotating device of the firstembodiment;

FIG. 1C is a diagram showing the rotating device of the firstembodiment;

FIG. 2 is a cross-sectional view taken along a line A-A in FIG. 1C;

FIG. 3 is an enlarged cross-sectional view showing the periphery of apassage of a lubricant in an enlarged manner from FIG. 2;

FIG. 4A is an enlarged cross-sectional view showing a cross section of ajoined portion of a rotating-body-side encircling member and a hub in anenlarged manner according to the first embodiment;

FIG. 4B is an enlarged cross-sectional view showing a cross section of ajoined portion of a rotating-body-side encircling member and a hub in anenlarged manner according to a first modified example of the firstembodiment;

FIG. 5 is an enlarged cross-sectional view showing the periphery of apassage of a lubricant of a rotating device in an enlarged manneraccording to a second modified example of the first embodiment;

FIG. 6 is an enlarged cross-sectional view showing the periphery of acylindrical magnet of the rotating device in an enlarged manneraccording to the second modified example;

FIG. 7 is a diagram showing a rotating device according to a secondembodiment of the present invention;

FIG. 8 is an enlarged cross-sectional view showing the periphery of apassage of a lubricant from FIG. 7 in an enlarged manner;

FIG. 9 is an enlarged cross-sectional view showing the periphery of apassage of a lubricant in an enlarged manner according to a firstmodified example of the second embodiment; and

FIG. 10 is an enlarged cross-sectional view showing a base member havinga shaft formed together with a base-side encircling member according toa second modified example of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be explained together with preferredembodiments thereof with reference to the accompanying drawings. Thesame or similar structural elements and members shown in respectivefigures are denoted by the same reference numeral, and the duplicatedexplanation will be omitted as needed. The dimension of a member in eachfigure is enlarged or scaled down accordingly in order to facilitateunderstanding for the present invention. Some of the members notimportant for explaining the detail of the present invention in eachfigure will be shown in an abbreviated manner.

The rotating devices of the embodiments are suitable as a disk drivedevice like a hard disk drive on which a magnetic recording disk isloaded and which rotates such a disk, in particular, a shaft-fixed typedisk drive device which has a shaft fixed to a base and which has a hubrotating relative to the shaft.

First Embodiment

FIGS. 1A to 1C are diagrams showing a rotating device 100 according to afirst embodiment. FIG. 1A is a top view of the rotating device 100. FIG.1B is a side view of the rotating device 100. FIG. 1C is a top view ofthe rotating device 100 with a top cover 2 being detached. The rotatingdevice 100 includes a fixed body, a rotating body that rotates relativeto the fixed body, a magnetic recording disk 8 that is attached to therotating body, and a data reading/writing unit 10. The fixed bodyincludes a base 4, a shaft 26 fixed to the base 4, the top cover 2, sixscrews 20, and a shaft fixing screw 6. The rotating body includes a hub28.

The explanation below will be given based on a definition that a sidewhere the hub 28 is mounted to the base 4 is an upper side.

The magnetic recording disk 8 is a 2.5 inch magnetic recording diskformed of a glass and having a diameter of 65 mm, and has a centeropening with a diameter of 20 mm and a thickness of 0.65 mm. The hub 28loads the two magnetic recording disks 8.

The base 4 is formed and shaped by die-casting on an aluminum alloy. Thebase 4 includes a bottom member 4 a forming the bottom of the rotatingdevice 100, and an external peripheral wall member 4 b formed along theexternal periphery of the bottom member 4 a so as to surround thelocation where the magnetic recording disks 8 are mounted. The externalperipheral wall member 4 b has six screw holes 22 formed in a top face 4c thereof.

The data reading/writing unit 10 includes a recording/playing head(unillustrated), a swing arm 14, a voice coil motor 16, and a pivotassembly 18. The recoding/playing head is attached to the tip of theswing arm 14, records data in the magnetic recording disks 8, and readsthe data therefrom. The pivot assembly 18 supports the swing arm 14 in aswingable manner to the base 4 around a head rotating shaft S. The voicecoil motor 16 allows the swing arm 14 to swing around the head rotatingshaft S to move the recording/playing head to a desired location overthe top face of the magnetic recording disk 8. The voice coil motor 16and the pivot assembly 18 are configured based on a conventionallywell-known technology of controlling the position of a head.

The top cover 2 is fixed to the top face 4 c of the external peripheralwall member 4 b of the base 4 using six screws 20. The six screws 20correspond to the six screw holes 22, respectively. In particular, thetop cover 2 and the top face 4 c of the external peripheral wall member4 b are fixed to each other so that no leak into the interior of therotating device 100 occurs at the joined portion therebetween. Theinterior of the rotating device 100 means, more specifically, a cleanspace 24 defined by the bottom member 4 a of the base 4, the externalperipheral wall member 4 b thereof, and the top cover 2. The clean space24 is designed so as to be hermetically closed, i.e., no leak-in fromthe exterior or no leak-out to the exterior occurs. The clean space 24is filled with clean air having particles eliminated. Hence, adhesion offoreign materials like particles to the magnetic recording disks 8 issuppressed, thereby increasing the reliability of the operation of therotating device 100.

The shaft 26 has a shaft fixing screw hole 26 a provided in a top endface. The shaft 26 has a bottom fixed to the base 4 by a technique to bediscussed later. The shaft fixing screw 6 passes all the way through thetop cover 2 and is screwed in the shaft fixing screw hole 26 a, and thusthe top end of the shaft 26 is fixed to the top cover 2. The top cover 2is fixed to the base 4.

Among the shaft-fixed type rotating devices, the rotating device thatfixes both ends of the shaft 26 to chassis, such as the base 4 and thetop cover, can improve the resistances against shock and vibration.According to the rotating device of this type, when a fluid dynamicbearing is used, in general, a lubricant has two air-liquid interfaces.According to the rotating device 100 of the present embodiment, insteadof simply arranging the two air-liquid interfaces and a dynamic pressuregenerating groove in a line in the direction of a rotation axis R (adirection along the rotation axis R), the passage of a lubricant isturned back so as to expand in the radial direction. Accordingly, thepassages of the lubricant partially overlap in the direction of therotation axis R. Hence, when the thickness of the rotating device 100 isrestricted, it is possible to increase the ratio of a portioncorresponding to the dynamic pressure generating groove to the wholethickness. As a result, the bearing span that is the dimension of thedynamic pressure generating groove in the axial direction is extended,thereby improving the rigidity of a bearing. Moreover, the distancebetween the two air-liquid interfaces can be reduced. As a result, theleak-out of the lubricant due to the gravity acting on the lubricant andthe pressure difference between the two air-liquid interfaces can besuppressed.

FIG. 2 is a cross-sectional view taken along a line A-A in FIG. 1C.

The rotating body includes the hub 28, a cylindrical magnet 32, arotating-body-side encircling member 104, an external-side encirclingmember 106, and a cap 12.

The fixed body includes the base 4, a stacked core 40, a coil 42, abase-side encircling member 102, the shaft 26, and a hub-side encirclingmember 108.

A lubricant 92 is continuously present in a part of the space betweenthe rotating body and the fixed body.

The magnetic recording disk 8 is mounted on a disk mounting face 28 a ofthe hub 28. The hub 28 is formed of an iron-and-steel material with asoft magnetic property like SUS430F. The hub 28 is formed by, forexample, pressing and cutting an iron-and-steel plate, and is formed ina predetermined shape like a cup having a center opening along therotation axis R. An example iron-and-steel material preferable for thehub 28 is stainless steel like one produced as DHS1 by DAIDO Steel Co.,Ltd., which has little out-gas, and is easy to process. Moreover,stainless steel with a production name DHS2 by the same company isfurther preferable due to a better corrosion resistance.

The cylindrical magnet 32 is bonded and fixed to a cylindrical innerperiphery 28 f corresponding to the internal cylindrical surface of thehub 28 in a cup-like shape. The cylindrical magnet 32 is formed of arare earth material, such as neodymium, iron, and born, and faces twelveprotrusions of the stacked core 40 in the radial direction. Polarizationwith 16 poles for driving is performed on the cylindrical magnet 32 inthe circumferential direction. A corrosion prevention treatment isperformed on the surface of the cylindrical magnet 32 byelectrodeposition coating, spray coating, etc.

The rotating-body-side encircling member 104 is a cylindrical memberthat encloses the shaft 26. The rotating-body-side encircling member 104has a radial dynamic pressure generating groove to be discussed laterprovided in an inner periphery 104 a of the rotating-body-sideencircling member 104. The rotating-body-side encircling member 104includes a first outer periphery 104 b, and a second outer periphery 104c which has a smaller diameter than the first outer periphery 104 b andwhich is provided under the first outer periphery 104 b. Therotating-body-side encircling member 104 has the first outer periphery104 b fitted in a center opening 28 b of the hub 28, and thus therotating-body-side encircling member 104 is fixed to the hub 28. Therotating-body-side encircling member 104 is bonded to the center opening28 b of the hub 28. A passage D of a lubricant 92 formed as a gapbetween the second outer periphery 104 c and the base-side encirclingmember 102 overlaps a passage B of the lubricant 92 formed as a gapbetween the inner periphery 104 a and (a side face 26 b of) the shaft 26in the direction of the rotation axis R.

The stacked core 40 includes an annular part and the twelve protrusionsextending therefrom outwardly in the radial direction, and is fixed tothe top face of the base 4. The stacked core 40 is formed by stacking,for example, 10 thin electromagnetic steel plates and integrating thosetogether by caulking. An insulative coating is performed on the surfaceof the stacked core 40 by electrodeposition coating, powder coating,etc. A coil 42 is wound around each protrusion of the stacked core 40.When a driving current of a substantially sine wave with three phasesflows through the coil 42, driving magnetic fluxes are generated alongthe protrusions.

The base 4 has a through hole 4 h provided along the rotation axis R ofthe rotating body. The base-side encircling member 102 has a crosssection substantially L-shape, and is bonded and fixed to the throughhole 4 h. The base-side encircling member 102 encloses the lower part ofthe shaft 26. That is, the base-side encircling member 102 has a shaftopening 102 a along the rotation axis R of the rotating body, and thebottom end of the shaft 26 is fitted in the shaft opening 102 a.

The bottom end of the shaft 26 is fixed to the base-side encirclingmember 102 by, in particular, interference fitting. Such interferencefitting is accomplished by, for example, pressing the shaft 26 in theshaft opening 102 a, shrink fitting, or inserting the shaft 26 cooled bya liquid nitrogen in the shaft opening 102 a, and then letting the shaft26 to be a normal temperature. It is fine if bonding is further appliedtogether with the interference fitting.

The base-side encircling member 102 includes a cylinder part 102 b in acylindrical shape that encloses the rotating-body-side encircling member104. A space between an inner periphery 102 ba of the cylinder part 102b and the second outer periphery 104 c of the rotating-body-sideencircling member 104 forms a passage D of the lubricant 92. A spacebetween an upper end face 102 bb of the cylinder part 102 b and a faceat the rotor side facing the end face 102 bb in the direction of therotation axis R forms a passage E of the lubricant 92. The cylinder partmay be formed separately from the base-side encircling member and may beattached thereto. When the cylinder part 102 b is formed together withthe other parts of the base-side encircling member 102 according to theembodiment of the present invention, the number of parts can be reduced.

A space between a bottom end face 104 d of the rotating-body-sideencircling member 104 and an opposing face 102 c of the base-sideencircling member 102 facing the end face 104 d in the direction of therotation axis R forms a passage C of the lubricant 92.

The external-side encircling member 106 is cylindrical which enclosesthe cylinder part 102 b and is fixed to the hub 28. Formed between theexternal-side encircling member 106 and the cylinder part 102 b is afirst capillary seal 110 that is a part where the space between an innerperiphery 106 a of the external-side encircling member 106 and an outerperiphery 102 bc of the cylinder part 102 b gradually becomes widespreaddownwardly. The first capillary seal 110 includes a first air-liquidinterface 112 of the lubricant 92, and prevents the lubricant 92 fromleaking out by a capillary phenomenon. The first air-liquid interface112 of the lubricant 92 contacts the outer periphery 102 bc of thecylinder part 102 b. In order to further suppress the leak-out of thelubricant 92, the first capillary seal 110 may have an area where anoil-repelling agent is applied around the outlet of such a seal.

The base 4 includes a cylindrical protrusion 4 e along the rotation axisR of the rotating body. The protrusion 4 e protrudes from the top faceof the base 4 so as to enclose the external-side encircling member 106.An outer periphery 4 ea of the protrusion 4 e is fitted in a centeropening 40 a of the annular part of the stacked core 40, and thus thestacked core 40 is fixed to the base 4. The annular part of the stackedcore 40 is bonded and fixed to the protrusion 4 e by, in particular,press-in or loose fit. The protrusion 4 e and the external-sideencircling member 106 form a labyrinth seal 66. Regarding the labyrinthseal 66, in particular, a thickness of a cylindrical space (a space gap)between an inner periphery 4 eb of the protrusion 4 e and the outerperiphery 106 b of the external-side encircling member 106 is set to beequal to or smaller than ⅕ of a height of the cylindrical space (alength of the cylindrical space), thereby suppressing a smooth flow ofair on some level. In this case, a vaporization of the lubricant 92 canbe suppressed, thereby extending the lifetime of the rotating device100.

The hub-side encircling member 108 encloses the upper part of the shaft26 and is fixed to the shaft 26. The hub-side encircling member 108 issubstantially cylindrical around the rotation axis R of the rotatingbody, and has a center opening 108 a where the shaft 26 is fitted. Thehub-side encircling member 108 is fixed to the shaft 26 by interferencefitting to the upper part of the shaft 26.

Formed between the hub-side encircling member 108 and the hub 28 is asecond capillary seal 114 that is a part where the space between a sealforming surface 28 d of the hub 28 and an outer periphery 108 b of thehub-side encircling member 108 gradually becomes widespread upwardly.The second capillary seal 114 has a second air-liquid interface 116 ofthe lubricant 92, and prevents the lubricant 92 from leaking out by acapillary phenomenon. In order to further suppress the leak-out of thelubricant 92, the second capillary seal 114 may have an area where anoil-repelling agent is applied around the outlet of such a seal.

A space between an upper end face 104 e of the rotating-body-sideencircling member 104 and an opposing face 108 c of the hub-sideencircling member 108 facing the end face 104 e in the direction of therotation axis R forms a passage A of the lubricant 92.

The cap 12 is an annular member which is fixed to the top face of thehub 28 so as to cover the second air-liquid interface 116 and thehub-side encircling member 108 and which has a cross section of areversed L-shape.

FIG. 3 is an enlarged cross-sectional view showing the periphery of thepassage of the lubricant 92 in an enlarged manner from FIG. 2. Formed inthe inner periphery 104 a of the rotating-body-side encircling member104 is a pair of first radial dynamic pressure generating groove 52 andsecond radial dynamic pressure generating groove 50 which are distantfrom each other in the direction of the rotation axis R and which are ina herringbone shape. The second radial dynamic pressure generatinggroove 50 is formed above the first radial dynamic pressure generatinggroove 52. At least one of the second radial dynamic pressure generatinggroove 50 and the first radial dynamic pressure generating groove 52 maybe formed in the side face 26 b of the shaft 26 instead of the innerperiphery 104 a of the rotating-body-side encircling member 104.

The passage B of the lubricant 92 includes a first gap 58 between aportion where the second radial dynamic pressure generating groove 50 isformed in the inner periphery 104 a of the rotating-body encirclingmember 104 and the side face 26 b of the shaft 26, and a second gap 60between a portion where the first radial dynamic pressure generatinggroove 52 is formed in the inner periphery 104 a of therotating-body-side encircling member 104 and the side face 26 b of theshaft 26.

When the rotating body rotates relative to the fixed body, the secondradial dynamic pressure generating groove 50 and the first radialdynamic pressure generating groove 52 generate dynamic pressures to thelubricant 92 in the first gap 58 and the second gap 60, respectively.Such dynamic pressures support the rotating body in the radial directionin a non-contact condition with the fixed body.

A first thrust dynamic pressure generating groove 54 in a herringbone orspiral shape is formed in the upper end face 104 e of therotating-body-side encircling member 104. The first thrust dynamicpressure generating groove 54 may be formed in the opposing face 108 cof the hub-side encircling member 108 instead of the upper end face 104e of the rotating-body-side encircling member 104.

A second thrust dynamic pressure generating groove 56 in a herringboneor spiral shape is formed in the bottom end face 104 d of therotating-body-side encircling member 104. The second thrust dynamicpressure generating groove 56 may be formed in the opposing face 102 cof the base-side encircling member 102 instead of the bottom end face104 d of the rotating-body-side encircling member 104.

The passage A of the lubricant 92 includes a third gap 62 between aportion where the first thrust dynamic pressure generating groove 54 isformed in the upper end face 104 e of the rotating-body-side encirclingmember 104 and the opposing face 108 c of the hub-side encircling member108.

The passage C of the lubricant 92 includes a fourth gap 64 between aportion where the second thrust dynamic pressure generating groove 56 isformed in the bottom end face 104 d of the rotating-body-side encirclingmember 104 and the opposing face 102 c of the base-side encirclingmember 102.

When the rotating body rotates relative to the fixed body, the firstthrust dynamic pressure generating groove 54 and the second thrustdynamic pressure generating groove 56 generate dynamic pressures to thelubricant 92 in the third gap 62 and the fourth gap 64, respectively.Such dynamic pressures support the rotating body in the direction of therotation axis R in a non-contact condition with the fixed body.

A distance L1 between the first air-liquid interface 112 of thelubricant 92 and the second air-liquid interface 116 thereof in thedirection of the rotation axis R is shorter than a distance L2 from anend 50 a of the second radial dynamic pressure generating groove 50opposite to the first radial dynamic pressure generating groove 52 to anend 52 a of the first radial dynamic pressure generating groove 52opposite to the second radial dynamic pressure generating groove 50.

The lubricant 92 is continuously present from the first air-liquidinterface 112 to the second air-liquid interface 116 through thepassages E, D, C, B, and A, in this order. In view of the dynamicpressure generating groove, the lubricant 92 is continuously presentfrom the first air-liquid interface 112 to the second air-liquidinterface 116 through the second thrust dynamic pressure generatinggroove 56, the first radial dynamic pressure generating groove 52, thesecond radial dynamic pressure generating groove 50, and the firstthrust dynamic pressure generating groove 54 in this order.

The first air-liquid interface 112 is located at thesecond-radial-dynamic-pressure-generating-groove-50 side over an end 52b of the first radial dynamic pressure generating groove 52 at thesecond-radial-dynamic-pressure-generating-groove-50 side in thedirection of the rotation axis R. In particular, the first air-liquidinterface 112 is located between the second radial dynamic pressuregenerating groove 50 and the first radial dynamic pressure generatinggroove 52 in the direction of the rotation axis R.

Next, an explanation will be given of an operation of the rotatingdevice 100 employing the above-explained configuration. A drive currentwith three phases is supplied to the coil 42 in order to rotate themagnetic recording disk 8. The drive current flowing through the coil 42generates magnetic fluxes along the twelve protrusions. The magneticfluxes provide torque to the cylindrical magnet 32, and thus therotating body and the magnetic recording disk 8 mounted thereon startrotating. Simultaneously, the voice coil motor 16 causes the swing arm14 to swing, and thus the recording/playing head moves in and out withinthe swing range over the magnetic recording disk 8. Therecording/playing head converts magnetic data recorded in the magneticrecording disk 8 into electronic signals, transmits such signals to anunillustrated control substrate, and writes data transmitted from thecontrol substrate as electronic signals in the magnetic recording disk8.

According to the rotating device 100 of the present embodiment, thedistance L1 is shorter than the distance L2. Hence, the first air-liquidinterface 112 and the second air-liquid interface 116 can be designed tobecome close to each other in the direction of the rotation axis R. Thisreduces the leak-out of the lubricant 92 due to gravity acting on thelubricant 92 and a difference in pressure between the first air-liquidinterface 112 and the second air-liquid interface 116. Moreover, thesecond radial dynamic pressure generating groove 50 and the first radialdynamic pressure generating groove 52 can be distant from each other inthe direction of the rotation axis R. Accordingly, the rigidity of thebearing can be improved.

Moreover, according to the rotating device 100 of the presentembodiment, the passage of the lubricant 92 is turned back so as toexpand in the radial direction, and the first air-liquid interface 112is located at the second-radial-dynamic-pressure-generating-groove-50side of the first radial dynamic pressure generating groove 52 beyondthe end 52 b at the second-dynamic-pressure-generating-groove-50 side inthe direction of the rotation axis R. This enables reduction of thethickness of the rotating device 100 in comparison with a case in whichone air-liquid interface, a radial dynamic pressure generating groove,and another air-liquid interface are arranged in this order along thedirection of the rotation axis R.

Furthermore, according to the rotating device 100 of the presentembodiment, when the passage of the lubricant 92 is turned back in theradial direction, portions where the rotating body and the fixed bodyface with each other in the direction of the rotation axis R, e.g.,portions corresponding to the passage A of the lubricant 92 and thepassage C thereof are spontaneously created. The rotating device 100 ofthe present embodiment has thrust dynamic pressure generating grooves atsuch portions.

Regarding the joined portion between the shaft and the base in ashaft-fixed type rotating device, it is desirable to fix the shaft bybonding in such a way that the perpendicularity of the shaft to the baseis adjustable. When, however, the diameter of the shaft is small,sufficient joining strength cannot be obtained in some cases by bonding.

According to the rotating device 100 of the present embodiment, theshaft 26 is interference fitted to the inner periphery of the base-sideencircling member 102, and the outer periphery is bonded to the base 4.Hence, when the outer periphery of the base-side encircling member 102is bonded to the base 4, it is possible to let the adhesive cured whilemaintaining the perpendicularity of the shaft 26 to the base 4appropriately. From the standpoint of the strength, since the shaft 26and the base-side encircling member 102 are joined together byinterference fitting, the joining strength thereof is sufficient, whileat the same time, since the diameter of the outer periphery of thebase-side encircling member 102 is large in comparison with the diameterof the shaft 26, the joining strength by bonding between the base-sideencircling member 102 and the base 4 is also sufficient.

According to the rotating device 100 of the present embodiment, thelabyrinth seal 66 is provided in a shape along the direction of therotation axis R. The hub 28 and the base 4 are present above and belowthe labyrinth seal 66, respectively. With reference to FIG. 3, when thethickness of the rotating device 100 is restricted, a total value(L3+L4+L5) of a length L3 of the labyrinth seal 66 in the direction ofthe rotation axis R, a thickness L4 of the portion of the hub 28 facingthe labyrinth seal 66 in the direction of the rotation axis R, and athickness L5 of the portion of the base 4 facing the labyrinth seal 66in the direction of the rotation axis R is restricted by the limitedthickness of the rotating device 100.

The rotating device 100 of the present embodiment has the length L3 ofthe labyrinth seal 66 set to be 1.93 mm in the direction of the rotationaxis R, the thickness L4 of the portion of the hub 28 to be equal to orlarger than 1.13 mm facing the labyrinth seal 66 in the direction of therotation axis R. In this case, the labyrinth seal 66 can furthersuppress a vaporization of the lubricant 92. Moreover, the thickness L5of the portion of the base 4 is set to be 3.07 mm facing the labyrinthseal 66 in the direction of the rotation axis R, and is larger than thelength L3 of the labyrinth seal 66 in the direction of the rotation axisR which is 1.93 mm. In this case, a deformation of the base 4 near thethrough hole 4 h due to vibration and shock can be further suppressed,and thus a small gap for the labyrinth seal 66 can be designed.

The explanation was given of the configuration and the operation of therotating device 100 according to the first embodiment. Theabove-explained embodiment is merely for exemplification, and it shouldbe understood by those skilled in the art that various modifications tothe combination of respective structural elements are possible and suchmodifications are within the scope and spirit of the present invention.

First Modified Example of First Embodiment

In manufacturing of the rotating device 100, the rotating-body-sideencircling member may wobble relative to the hub. In order to preventthe rotating-body-side encircling member from wobbling relative to thehub, facilities may be devised or an employment of a skilled worker maybe necessary. However, devising of the facilities needs a cost and isoften difficult. Moreover, it is not always true that the skilled workeris placed in the manufacturing line. Hence, in this case, the hub andthe rotating-body-side encircling member are devised in order to employa configuration in which the hub and the rotating-body-side encirclingmember easily become coaxial to each other.

FIGS. 4A and 4B are enlarged cross-sectional views showing a crosssection of a joined part of the rotating-body-side encircling member andthe hub according to the first embodiment and a first modified examplethereof, respectively. FIG. 4A is an enlarged cross-sectional viewshowing an area surrounded by a dashed circle in FIG. 2 in an enlargedmanner. FIG. 4B is an enlarged cross-sectional view showing a partcorresponding to FIG. 4A of a rotating device according to the firstmodified example. According to the rotating device of the first modifiedexample, a surface at the hub-228 side in the surface where arotating-body-side encircling member 204 and a hub 228 are joinedtogether includes a cylindrical first periphery 250 and adiameter-increasing surface 256 increasing the diameter from a lowerperipheral end 250 a of the first periphery 250 toward the bottom. Asurface at the rotating-body-side-encircling-member-204 side in thesurface where the rotating-side-encircling member 204 and the hub 228are joined together includes a cylindrical second periphery 252 and athird periphery 254 which is formed below the second periphery 252 andwhich has a larger diameter than that of the second periphery 252. Thefirst periphery 250 and the second periphery 252 abut with each other,and are in particular bonded together. A step 258 formed between thesecond periphery 252 and the third periphery 254 abuts thediameter-increasing surface 256. That is, the step 258 is in linecontact with the diameter-increasing surface 256.

In this case, when the rotating-body-side encircling member 204 isbonded to the hub 228, the step 258 abuts the diameter-increasingsurface 256. Accordingly, the tilting of the rotating-body-sideencircling member 204 relative to the hub 228 is suppressed, and thecoaxiality of the hub 228 and the rotating-body-side encircling member204 can be ensured.

It is also appropriate if the second periphery and the third peripheryare provided in a surface at the hub side in the surface where therotating-body-side encircling member and the hub are joined together,and the first periphery and the diameter-increasing surface are providedin a surface at the rotating-body-side-encircling-member side in thesurface where the rotating-body-side encircling member and the hub arejoined together.

According to the above-explained embodiment, the hub 28 and therotating-body-side encircling member 104 are first separately formed andjoined together later, but the present invention is not limited to thisconfiguration. For example, the hub 28 and the rotating-body-sideencircling member 104 may be integrally formed together. In this case,an outer periphery 28 g of the hub 28 and an inner periphery 104 a ofthe rotating-body-side encircling member 104 may be successively cut andmachined. Inconsistency of the center of the outer periphery 28 g of thehub 28 and that of the inner periphery 104 a of the rotating-body-sideencircling member 104 can be easily suppressed.

In the above-explained embodiment, the explanation was given of the casein which the first air-liquid interface 112 and the second air-liquidinterface 116 do not overlap in the radial direction, but the presentinvention is not limited to this configuration. For example, oneair-liquid interface may be provided so as to at least partially overlapanother air-liquid interface. In this case, respective positions in theradial direction of the two air-liquid interfaces when inverted upsidedown become substantially same. Hence, a needle can be commonly usedwhen a lubricant is filled in the gap spaces forming respectiveair-liquid interfaces, and the lubricant can be filled in the two gapspaces by inverting the rotating device upside down with the needlebeing substantially still. That is, the lubricant can be appropriatelyfilled in the gap spaces forming the two air-liquid interfaces usingonly one needle.

According to the above-explained embodiment, the explanation was givenof the case in which no communicating passage for letting the firstcapillary seal 110 and the second capillary seal 114 communicated witheach other is provided, but the present invention is not limited to thisconfiguration. For example, a communicating passage for letting thefirst capillary seal 110 and the second capillary seal 114 communicatedwith each other may be provided without through both of the secondradial dynamic pressure generating groove 50 and the first radialdynamic pressure generating groove 52. Moreover, a communicating passagefor letting the first capillary seal 110 and the second capillary seal114 communicated with each other linearly may be provided. For example,with reference to FIG. 3, a groove along the axial direction may beprovided in the first outer periphery 104 b of the rotating-body-sideencircling member 104 abutting the hub 28 in order to form acommunicating passage. Since a difference in pressure between the firstcapillary seal 110 and the second capillary seal 114 becomes small, theleak-out of the lubricant 92 can be suppressed.

Second Modified Example of First Embodiment

Next, an explanation will be given of a second modified example of thefirst embodiment with reference to FIGS. 5 and 6. Depending on theapplication of the rotating device 100, it is necessary to suppress aleak-out of the lubricant 92 at a higher level. Moreover, a precisionfor the position of the rotating body is required in some cases. Inorder to apply the rotating device in such an application, a followingconfiguration that modifies the above-explained configuration can beemployed. FIG. 5 is an enlarged cross-sectional view showing theperiphery of the air-liquid interface of the lubricant in an enlargedmanner according to a second modified example. FIG. 5 shows a crosssection leftward from the rotation axis R, and the right cross sectionis symmetrical with the left cross section. FIG. 6 is an enlargedcross-sectional view showing the periphery of a cylindrical magnet 32 inan enlarged manner according to the second modified example. The secondmodified example employs the same configuration as that of FIG. 2 otherthan the portions shown in FIGS. 5 and 6.

In the above explanation, the explanation was given of the case in whichthe second air-liquid interface 116 of the lubricant 92 contacts theouter periphery of the hub-side encircling member 108. According to thesecond modified example, a second air-liquid interface 216 of thelubricant 92 contacts the inner periphery of the rotating-body-sideencircling member 104 and the outer periphery of the shaft 26. Thesecond modified example includes no hub-side encircling member 108. Thisresults in the reduction of the number of the parts, thereby reducingthe work and effort for assembling. Moreover, the accumulation ofdimension errors at the time of assembling of the parts can be reduced.

According to the second modified example shown in FIG. 5, the firstouter periphery 104 b of the rotating-body-side encircling member 104contacting the hub 28 slightly protrudes outwardly of the radialdirection from an outer periphery 102 bc of the cylinder part 102 b ofthe base-side encircling member 102. In other words, the diameter of thefirst outer periphery 104 b is larger than that of the outer periphery102 bc. The rotating-body-side encircling member 104 has the first outerperiphery 104 b fixed to the center opening 28 b of the hub 28 by bothpress fitting and bonding.

The shaft 26 is formed with a shaft periphery 26 ba that is a side facereducing a diameter toward the opposite direction to the base 4 in theaxial direction. The shaft periphery 26 ba is located above the area ofthe side face 26 b where the second radial dynamic pressure generatinggroove 50 is provided. The rotating-body-side encircling member 104 isformed with a second inner periphery 104 j that is a side face reducinga diameter toward the opposite direction to the base 4 in the axialdirection. The second inner periphery 104 j is located at a portion nearthe upper end of the rotating-body-side encircling member 104. Thesecond inner periphery 104 j is located so as to encircle and partiallyoverlap the shaft periphery 26 ba. An inclined angle of the shaftperiphery 26 ba relative to the rotation axis R is larger than aninclined angle of the second inner periphery 104 j relative to therotation axis R. The gap between the second inner periphery 104 j andthe shaft periphery 26 ba gradually becomes wide toward the upper partalong the rotation axis R. The gap between the second inner periphery104 j and the shaft periphery 26 ba forms a capillary seal 214. Oneair-liquid interface 216 of the lubricant 92 is located between theshaft periphery 26 ba and the second inner periphery 104 j. That is, theair-liquid interface 216 contacts the second inner periphery 104 j andthe shaft periphery 26 ba. An unillustrated oil-repelling agent isapplied to the upper end of the second inner periphery 104 j and that ofthe shaft periphery 26 ba, thereby reducing the leak-out of thelubricant 92.

The rotating-body-side encircling member 104 is provided with a pathway104 h for letting the lubricant 92 contacting the inner periphery sideof the rotating-body-side encircling member 104 and the lubricant 92contacting the outer periphery side thereof communicated with eachother. The pathway 104 h is provided so as to pass all the way throughthe rotating-body-side encircling member 104 from the inner periphery104 a to the outer periphery 104 k. The pathway 104 h is located so asto communicate a space between the first capillary seal 110 and thesecond capillary seal 214. More specifically, the pathway 104 h islocated between the second inner periphery 104 j and the first gap 58 inthe direction of the rotation axis R. The pathway 104 h reduces adifference in pressure between the first capillary seal 110 and thesecond capillary seal 214, thereby suppressing the leak-out of thelubricant 92.

A single pathway 104 h is provided but a plurality of pathways 104 h maybe provided in the circumferential direction. The distribution of radialdynamic pressures in the circumferential direction becomes non-uniformdue to the pathway 104 h. Hence, it is appropriate if a plurality ofpathways 104 h are arranged in the circumferential direction at an equalinterval. This suppresses the non-uniformity of the distribution ofradial dynamic pressures in the circumferential direction. According tothe second modified example, two pathways 104 h are provided insymmetrical locations with reference to the rotation axis R.

A distance L1 between the first air-liquid interface 112 of thelubricant 92 and the second air-liquid interface 216 thereof in thedirection of the rotation axis R is shorter than a distance L2 from theend 50 a of the second radial dynamic pressure generating groove 50opposite to the first radial dynamic pressure generating groove 52 tothe end 52 a of the first radial dynamic pressure generating groove 52opposite to the second radial dynamic pressure generating groove 50.

A dynamic pressure generating groove that generates dynamic pressure inthe thrust direction can be formed in either one of the bottom end face104 d of the rotating-body-side encircling member 104 and the opposingface 102 c of the base-side encircling member 102. Moreover, anothergroove that generates dynamic pressure in the thrust direction can beformed in either one of the end face 102 bb of the cylinder part 102 band a rotating-body-side opposing face 104 g of the rotating-body-sideencircling member 104 facing the end face 102 bb in the axial direction.The dynamic pressure generating groove that generates dynamic pressurein the thrust direction can be formed in a herringbone shape or a spiralshape. In the case of the second modified example shown in FIG. 5, athird dynamic pressure generating groove 57 is formed in therotating-body-side opposing face 104 g in a spiral shape. In FIG. 5, aletter G denotes the center of gravity of the rotating body when themagnetic recording disk 8 is mounted thereon. The position of therotating-body-side opposing face 104 g in the direction of the rotationaxis R is formed above the gravity center G. As a result, the rotatingbody is supported circumferentially by an area above the gravity centerG, and thus the rotating body is not likely to tilt.

FIG. 6 is an enlarged cross-sectional view showing the periphery of thecylindrical magnet 32 of the rotating device in an enlarged manneraccording to the second modified example. According to the secondmodified example, a suction plate 41 is fastened near a bottom end face32 a of the cylindrical magnet 32 and on the top face of the base 4. Theother portions are same as those shown in FIG. 2. The suction plate 41may be fastened by, for example, bonding. The outer periphery surface ofthe suction plate 41 faces a side face 4 m of the step of the base 4 inthe radial direction. The bottom end face of the suction plate 41 ismounted on a plate mounting part 4 k of the base 4. The suction plate 41is formed of a tabular member of a magnetic material like an iron and ina ring shape.

The third dynamic pressure generating groove 57 generates dynamicpressure to the lubricant 92 in a pump-in direction, and upward force tothe rotating body is produced. Moreover, the suction plate 41magnetically suctions the cylindrical magnet 32. As a result, downwardforce to the rotating body including the cylindrical magnet 32 is alsoproduced. The rotating body is stabilized at a position where the upwardforce is balanced with the downward force and the gravitational forceacting on the rotating body. That is, in the direction along therotation axis R, the position of the rotating body with reference to thefixed body can be defined by setting the downward force in accordancewith the upward force and the gravitational force acting on the rotatingbody.

Next, an explanation will be given of the external-side encirclingmember 106. In the case of the example shown in FIG. 3, the explanationwas given of the external-side encircling member 106 which is formedseparately from the hub 28 and which is fixed thereto later, but thepresent invention is not limited to this configuration. According to thesecond modified example shown in FIG. 5, the external-side encirclingmember 106 is formed integrally with the hub 28. A high dimensionaccuracy can be easily obtained for the inner periphery of theexternal-side encircling member 106, and it is also preferable from thestandpoint of less assembling work and effort.

According to the second modified example shown in FIG. 5, the cap 12 isprovided so as to cover at least a part of the second air-liquidinterface 216 and the upper end of the rotating-body-side encirclingmember 104. The side face of the outer circumference of the cap 12contacts the side face of the center opening 28 b of the hub 28. Thebottom end face of the cap 12 contacts the upper end face of therotating-body-side encircling member 104. The cap 12 is an annularmember in a substantially disc shape. It is preferable since a highdimension accuracy can be obtained.

According to the above-explained embodiment, the explanation was givenof the case in which the base-side encircling member 102 is directlyattached to the base 4, but the present invention is not limited to thisconfiguration. For example, a brushless motor including a rotating bodyand a fixed body may be separately formed and such a brushless motor maybe attached to a chassis.

Second Embodiment

Depending on the specification of a product using the rotating device,it is desirable to reduce the cost of the whole product whileaccomplishing the above-explained object. Filling of a lubricant is arequisite process in manufacturing of the rotating device, but if such arequisite process can be simplified, the cost of the rotating device canbe reduced, thereby reducing the cost of the whole product. Anexplanation below will be given in detail of a rotating device of asecond embodiment which employs a configuration appropriate for such anapplication with reference to the accompanying drawings.

Like the first embodiment, a rotating device of the second embodiment isalso a shaft-fixed type disk drive device. The same structural elementas that of the first embodiment will be denoted by the same referencenumeral, and the detailed explanation thereof will be omitted forclarity. The explanation below will be mainly given of the differentpart from the first embodiment.

FIG. 7 is a cross-sectional view showing a rotating device 200 of thesecond embodiment. A rotating body includes a hub 28, a cylindricalmagnet 32, a rotating-body-side encircling member 105, an external-sideencircling member 206, and a cap 12. A fixed body includes a base 4, astacked core 40, a coil 42, a base-side encircling member 102, a shaft26, and a hub-side encircling member 108. A lubricant 92 is continuouslypresent partially in a space between the rotating body and the fixedbody.

According to the rotating device 200 of the present embodiment, a firstmagnetic center 321 that is a center of the driving magnetization by thecylindrical magnet 32 in the direction of the rotation axis R is locatedso as to be substantially consistent with a second magnetic center 401that is a center of the stacked core 40 in the direction of the rotationaxis R. It is preferable since noises at the time of rotation due to thedriving magnetization by the cylindrical magnet 32 and the stacked core40 can be suppressed. The first magnetic center 321 may be located abovethe second magnetic center 401 and distant therefrom. This enables anincrease of the dimension of the cylindrical magnet 32 in the axialdirection, and thus driving torque generated by the cylindrical magnet32 increases.

In a condition in which the hub 28 is downwardly directed to the base 4,the hub 28 may be descended by gravitational force but may be toodistant from the base 4 during a rotation, which disturbs a normalrotation. In order to address this problem, a suction plate 141 isbonded and fixed to the base 4 at a location facing the bottom end ofthe cylindrical magnet 32. The suction plate 141 is formed of a materialmainly containing, for example, iron and having a soft magneticproperty. The suction plate 141 produces magnetic suction force to themagnet 32. The suction plate 141 is formed in a substantially ringshape, and the diameter of the inner circumference of such a ring shapemay be larger than the diameter of the inner circumference of thecylindrical magnet 32. This increases the ratio of magnetic fluxesreceived by the stacked core 40 among magnetic fluxes generated by thecylindrical magnet 32.

The rotating-body-side encircling member 105 is cylindrical whichencircles the shaft 26. An inner cylinder 1051 which has an innerperiphery encircling the shaft 26 and an outer cylinder 1052 whichencircles the inner cylinder 1051 are formed separately, and bonded andfixed together in order to form the rotating-body-side encircling member105. The inner cylinder 1051 has an inner periphery 1051 a provided witha radial dynamic pressure generating groove to be discussed later. Acommunicating passage BP that is a groove along the direction of therotation axis R is provided in the outer periphery of the inner cylinder1051. The communicating passage BP is filled with a lubricant 92, andlets a passage A′ and a passage C′ to be discussed later communicatedwith each other. The communicating passage BP reduces a difference inpressure between the passage A′ and the passage C′, thereby suppressinga leak-out of the lubricant 92 from the air-liquid interface. Thecommunicating passage BP may be provided as a groove along the axialdirection in the inner periphery of the outer cylinder 1052.

The base 4 is provided with a through hole 4 h around the rotation axisR of the rotating body. The base-side encircling member 102 includes adisk part 102 d that encircles the base-4 side of the shaft 26 and acylinder part 102 b that encircles the rotating-body-side encirclingmember 105. That is, the base-side encircling member 102 has asubstantially L-shaped cross section. An outer periphery 102 bd of thecylinder part 102 b is bonded and fixed to the through hole 4 h. Thebase-side encircling member 102 has a shaft opening 102 a around therotation axis R of the rotating body, and the bottom end of the shaft 26is fitted in the shaft opening 102 a.

The base 4 includes a cylindrical protrusion 4 e around the rotationaxis R of the rotating body. The protrusion 4 e protrudes from the topface of the base 4 so as to encircle the cylinder part 102 b. A centeropening 40 a of the annular part of the stacked core 40 is fitted withan outer periphery 4 ea of the protrusion 4 e, and thus the stacked core40 is fixed to the base 4. The annular part of the stacked core 40 isbonded and fixed to the protrusion 4 e by, in particular, press fittingor loose fitting.

FIG. 8 is an enlarged cross-sectional view showing the periphery of apassage of the lubricant 92 in FIG. 7 in an enlarged manner. The outercylinder 1052 has an encircling recess 1052 bb provided at the middlepart of an outer periphery 1052 b in the direction of the rotation axisR and recessed inwardly in the radial direction. The outer periphery1052 b of the outer cylinder 1052 is fitted into a hub opening 28 b ofthe hub 28, and thus the outer cylinder 1052 is fixed to the hub 28. Thehub-28 side of the outer periphery 1052 b of the outer cylinder 1052 isbonded to the hub opening 28 b of the hub 28. A circumferential grooveis formed in the part of the outer periphery 1052 b fixed to the hubopening 28 b. A passage D′ of the lubricant 92 formed as a gap betweenthe outer periphery 1052 b and the base-side encircling member 102overlaps a passage B′ of the lubricant 92 formed as a gap between theinner periphery 104 a and a side face 26 b of the shaft 26 in thedirection of the rotation axis R.

The shaft 26 has a bottom end fixed to the disk part 102 d of thebase-side encircling member 102 by, in particular, interference fitting.Such an interference fitting can be realized by, for example, pressingthe shaft 26 into the shaft opening 102 a, shrink fitting, or insertingthe shaft 26 cooled by a liquid nitrogen in the shaft opening 102 a andthen letting the shaft 16 to be a normal temperature. It is appropriateif bonding is applied together with the interference fitting.

The base-side encircling member 102 has a portion where the cylinderpart 102 b contacts the through hole 4 h larger than a portion where thedisk part 102 d contacts the shaft 26 in the axial direction.

The cylinder part 102 b may be separately formed from the disk part 102d and joined together later. When the cylinder part 102 b and the diskpart 102 d are formed integrally with each other like the presentembodiment, the number of parts can be reduced. A gap between the innerperiphery 102 ba of the cylinder part 102 b and the outer periphery 1052b of the outer cylinder 1052 forms a passage D′ of the lubricant 92. Agap between a first thrust surface 1051 d that is a bottom end face ofthe inner cylinder 1051 and a first opposing face 102 c of the base-sideencircling member 102 facing such a thrust surface in the direction ofthe rotation axis R forms a passage C′ of the lubricant 92. The firstopposing face 102 c is provided on the disk part 102 d.

A first capillary seal 210 is formed where a gap between the innerperiphery 102 ba of the cylinder part 102 b and the outer periphery 1052b of the outer cylinder 1052 gradually becomes widespread upwardly. Thefirst capillary seal 210 has a first air-liquid interface 312 of thelubricant 92, and prevents the lubricant 92 from leaking out by acapillary phenomenon. The first air-liquid interface 312 of thelubricant 92 contacts the inner periphery 102 ba of the cylinder part102 b and the outer periphery 1052 b of the outer cylinder 1052. Inorder to further suppress a leak-out of the lubricant 92, the firstcapillary seal 210 may have an area where an oil-repelling agent isapplied around the outlet of such a seal.

When, for example, the rotating device receives shock, the lubricant 92may spill out from the first air-liquid interface 312. In order toaddress this problem, a reservoir 115 is provided which is a pouchedspace having an opening at a location facing the first air-liquidinterface 312 in the direction of the rotation axis R. The lubricant 92spilled out from the first air-liquid interface 312 is caught in thereservoir 115, thereby suppressing a leak to the exterior. The reservoir115 is formed between the hub 28 and the outer cylinder 1052. Morespecifically, the reservoir 115 is formed in a space between the hubopening 28 b and the outer periphery 1052 b. An oil-repelling agent maybe applied to the reservoir 115. This further suppresses a leak-out ofthe lubricant 92. The reservoir 115 may be provided at a portion wherethe gap between the hub opening 28 b and the encircling recess 1052 bbgradually becomes widespread downwardly. The concavity of the encirclingrecess 1052 bb increases the spatial volume of the reservoir 115, whichcan suppress a leak to the exterior when a large amount of the lubricant92 spills out.

The external-side encircling member 206 is cylindrical which encirclesthe hub-side encircling member 108 and which is fixed to the outercylinder 1052. The external-side encircling member 206 is bonded andfixed to a step 1053 c provided above the inner periphery of the outercylinder 1052. An adhesive 120 is applied across the external-sideencircling member 206 and the outer cylinder 1052. The external-sideencircling member 206 may be fixed by other conventionally well-knowntechniques like press fitting. Formed between the external-sideencircling member 206 and the hub-side encircling member 108 is a secondcapillary seal 314 that is a portion where a gap between an innerperiphery 206 a of the external-side encircling member 206 and an outerperiphery 108 b of the hub-side encircling member 108 gradually becomeswidespread upwardly. The second capillary seal 314 has a secondair-liquid interface 316 of the lubricant 92, and suppresses a leak-outof the lubricant 92 by a capillary phenomenon. The second air-liquidinterface 316 of the lubricant 92 contacts the inner periphery 206 a ofthe external-side encircling member 206 and the outer periphery 108 b ofthe hub-side encircling member 108. In order to further suppress aleak-out of the lubricant 92, the second capillary seal 314 may have anarea where an oil-repelling agent is applied around the outlet of such aseal.

A gap between an upper second thrust surface 1051 e of the innercylinder 1051 and the second opposing face 108 c of the hub-sideencircling member 108 facing such a thrust surface in the direction ofthe rotation axis R forms a passage A′ of the lubricant 92. The secondopposing face 108 c is provided on the hub-side encircling member 108.

The cap 12 is an annular member in a disk shape, and has an outerperiphery fixed to the hub opening 28 b of the hub 28. The cap 12 isprovided so as to cover the second air-liquid interface 316 and thehub-side encircling member 108. The cap 12 has a bottom end facecontacting the upper end face of the outer cylinder 1052.

A pair of herringbone first and second radial dynamic pressuregenerating grooves 150 and 152 are formed in the inner periphery 1051 aof the inner cylinder 1051 so as to be distant from each other in thedirection of the rotation axis R. The second radial dynamic pressuregenerating groove 152 is formed above the first radial dynamic pressuregenerating groove 150. At least either one of the first and secondradial dynamic pressure generating grooves 150 and 152 may be formed inthe side face 26 b of the shaft 26 instead of the inner periphery 1051a.

A passage B′ of the lubricant 92 includes a gap between a portion of theinner periphery 1051 a of the inner cylinder 1051 where the first radialdynamic pressure generating groove 150 is formed and the side face 26 bof the shaft 26, and a gap between a portion of the inner periphery 1051a of the rotating-body-side encircling member 105 (the inner cylinder1051) where the second radial dynamic pressure generating groove 152 isformed and the side face 26 b of the shaft 26.

When the rotating body rotates relative to the fixed body, the firstradial dynamic pressure generating groove 150 and the second dynamicpressure generating groove 152 generate respective dynamic pressures tothe lubricant 92 in respective gaps. Such dynamic pressures support therotating body in the radial direction in a non-contact condition withthe fixed body.

A herringbone or spiral first thrust dynamic pressure generating groove156 is formed in the lower first thrust surface 1051 d of the innercylinder 1051. The first thrust dynamic pressure generating groove 156may be formed in the first opposing face 102 c of the base-sideencircling member 102 instead of the first thrust surface 1051 d.

A herringbone or spiral second thrust dynamic pressure generating groove154 is formed in the upper second thrust surface 1051 e of the innercylinder 1051. The second thrust dynamic pressure generating groove 154may be formed in the second opposing face 108 c of the hub-sideencircling member 108 instead of the second thrust surface 1051 e.

The passage C′ of the lubricant 92 includes a gap between a portion ofthe lower first thrust surface 1051 d of the inner cylinder 1051 wherethe first thrust dynamic pressure generating groove 156 is formed andthe first opposing face 102 c of the base-side encircling member 102.

The passage A′ of the lubricant 92 includes a gap between a portion ofthe upper second thrust surface 1051 e of the inner cylinder 1051 wherethe second thrust dynamic pressure generating groove 154 is formed andthe second opposing face 108 c of the hub-side encircling member 108.

When the rotating body rotates relative to the fixed body, the secondand first dynamic pressure generating grooves 154 and 156 generaterespective dynamic pressures to the lubricant 92 in respective gaps.Such dynamic pressures support the rotating body in the direction of therotation axis R in a non-contact condition with the fixed body.

A distance L1′ between the first air-liquid interface 312 of thelubricant 92 and the second air-liquid interface 316 thereof in thedirection of the rotation axis R is shorter than a distance L2′ betweenan end 150 a of the first radial dynamic pressure generating groove 150opposite to the second radial dynamic pressure generating groove 152 andan end 152 a of the second radial dynamic pressure generating groove 152opposite to the first radial dynamic pressure generating groove 150.

The lubricant 92 is continuously present from the first air-liquidinterface 312 to the second air-liquid interface 316 through thepassages D′, C′, B′, and A′, in this order. In view of the dynamicpressure generating groove, the lubricant 92 is continuously presentfrom the first air-liquid interface 312 to the second air-liquidinterface 316 through the first thrust dynamic pressure generatinggroove 156, the first radial dynamic pressure generating groove 150, thesecond radial dynamic pressure generating groove 152, and the secondthrust dynamic pressure generating groove 154 in this order.

The first air-liquid interface 312 is located at thesecond-radial-dynamic-pressure-generating-groove-152 side over an end150 b of the first radial dynamic pressure generating groove 150 at thesecond-radial-dynamic-pressure-generating-groove-152 side in thedirection of the rotation axis R. In particular, the first air-liquidinterface 312 is located between the first radial dynamic pressuregenerating groove 150 and the second radial dynamic pressure generatinggroove 152 in the direction of the rotation axis R.

Next, an explanation will be given of a manufacturing method of therotating device 200 according to the second embodiment.

First, the base-side encircling member 102 is joined with the shaft 26.Moreover, the inner cylinder 1051 having predetermined dynamic pressuregenerating grooves formed at the inner periphery 1051 a, the firstthrust surface 1051 d and the second thrust surface 1051 e is joinedwith the outer cylinder 1052. Next, the shaft 26 is inserted in theinner periphery 1051 a of the inner cylinder 1051. Thereafter, thehub-side encircling member 108 is joined at a predetermined upperlocation of the shaft 26. The external-side encircling member 206 isjoined with a step 1052 c of the outer cylinder 1052. The assembly inthis condition is hereinafter referred to as a bearing assembly. Next,the bearing assembly is revealed in a reduced-pressure condition inorder to remove air in the gap between the fixed body and the rotatingbody. Under the reduced-pressure condition, a predetermined amount ofthe lubricant 92 is applied to the gap between the external-sideencircling member 206 and the hub-side encircling member 108 and the gapbetween the base-side encircling member 102 and the outer cylinder 1052.For example, the lubricant 92 can be applied thereto by discharging thelubricant 92 from a discharging nozzle moved close to the target. Next,the bearing assembly is returned to an atmospheric pressure condition inorder to let the lubricant 92 to permeate the interior of the bearingassembly. As a result, the lubricant 92 permeates the gap between thefixed body and the rotating body and is present therebetween.

Next, respective positions of the first air-liquid interface 312 and thesecond air-liquid interface 316 in the direction of the rotation axis Rare inspected in the bearing assembly. Respective positions of theair-liquid interfaces can be inspected by emitting laser light to theair-liquid interfaces and by checking reflected light. According to therotating device 200 of the second embodiment, in the condition as thebearing assembly, the first air-liquid interface 312 and the secondair-liquid interface 316 can be visually checked from the samedirection. Hence, respective positions of the first air-liquid interface312 and the second air-liquid interface 316 can be inspected by emittinglaser light from the same direction. Accordingly, such an inspectionneeds no inversion of the bearing assembly upside down, whichcontributes to the downsizing of an inspection device, and to littlework and effort for the inspection.

Conversely, the cylindrical magnet 32 is bonded and fixed to acylindrical inner periphery 28 f of substantially the cup-shaped hub 28.Moreover, the stacked core 40 with the coil 42 is bonded and fixed to anouter periphery 4 ea of the base 4.

Next, the outer periphery 1052 b of the outer cylinder 1052 of therotating-body-side encircling member 105 is bonded and fixed to the hubopening 28 b of the hub 28. Thereafter, the outer periphery 102 bd ofthe base-side encircling member 102 is bonded and fixed to the throughhole 4 h. At this time, an adhesive is let cured while the tilting of adisk mounting face 28 a of the hub 28 to the base 4 is maintained to anappropriate level. As a result, the tilting of the disk mounting face 28a of the hub 28 to the base 4 can be suppressed.

Next, other members are mounted, and a predetermined inspection isperformed on the assembly, thereby manufacturing the rotating device200.

The rotating device 200 employing the above-explained configuration hasthe same operation as that of the first embodiment. That is, such aconfiguration also can reduce the leak-out of the lubricant 92 due tothe gravitational force acting on the lubricant 92 and a difference inpressure between the first air-liquid interface 312 and the secondair-liquid interface 316. Moreover, the first radial dynamic pressuregenerating groove 152 and the second radial dynamic pressure generatinggroove 150 can be distant from each other in the direction of therotation axis R, increasing the rigidity of the bearing.

First Modified Example of Second Embodiment

It is an essential fact whether or not a lubricant is correctly filledin manufacturing of rotating devices. Hence, inspection of the lubricantis always carried out, but depending on the specification of a rotatingdevice, in order to deal with a manufacturing cost, a simplification ofsuch an inspection is further desired. A first modified example belowemploys a configuration that further simplifies the inspection of thelubricant.

FIG. 9 is an enlarged cross-sectional view showing in an enlarged mannerthe periphery of a passage of a lubricant in a modified example 300 ofthe rotating device according to the second embodiment. According to themodified example 300, a portion of the outer cylinder 1052 contactingthe hub opening 28 b has a smaller diameter than a diameter of theinnermost circumference of the first air-liquid interface 312.

That is, the innermost circumference of the first air-liquid interface312 is located outwardly of the radial direction beyond the outermostcircumference of a part of the outer cylinder 1052 contacting the hubopening 28 b. As a result, before the hub 28 is fixed to the outercylinder 1052, the first air-liquid interface 312 can be visuallychecked easily from the above. When it is inspected whether or not thelubricant 92 is insufficient, since visual checking is facilitated, thework and effort for such an inspection are little. Moreover, when laserlight is emitted to inspect the position of the first air-liquidinterface 312 in the axial direction, alignment of the laser light iseasy, and thus the work and effort for such an inspection are little.

Moreover, the upper end of the external-side encircling member 206 islocated above the upper end of the outer cylinder 1052. This results inreduction of a possibility that an adhesive 120 applied across the outercylinder 1052 and the external-side encircling member 206 goes over theupper end of the external-side encircling member 206 and flows in acapillary seal 314. The adhesive 120 may be applied across theexternal-side encircling member 206, the outer cylinder 1052, and thehub 28.

Second Modified Example of Second Embodiment

According to the second embodiment and the above modified example, theexplanation was given of the case in which the shaft 26 is formedseparately from the base-side encircling member 102, but the presentinvention is not limited to this configuration. FIG. 10 is an enlargedcross-sectional view showing a base-side member 140 including the shaft26 formed integrally with the base-side encircling member 102 in themodified example 300 of FIG. 9. Since the number of parts can bereduced, the work and effort for assembling become little. Moreover,when the rotating device is formed to be thin, a high joined strengthbetween the shaft 26 and the base-side encircling member 102 can beensured.

In the example case shown in FIG. 10, the base-side member 140 is formedas a single piece from a stainless-steel material equivalent to JIS(Japanese Industrial Standards) SUS 430 by pressing, and the detailsthereof are finished by cutting, grinding, etc. The base-side member 140may be formed of other materials and by other techniques in order tomeet a desired specification. The shaft 26 is provided with a throughhole 140 b by pressing. A shaft fixing screw hole 26 a is formed in theupper end side of the through hole 140 b. A protrusive reinforced part140 a that increases the diameter is formed in a coupled part of theshaft 26 and the base-side encircling member 102. This suppresses adeformation of the coupled part when the rotating device 200 receivesshock.

Other Modified Examples

The rotating devices according to the embodiments of the presentinvention were explained above. However, it should be understood forthose skilled in the art that such embodiments are only to give anexplanation, and various changes and modifications can be made withinthe scope and spirit of the present invention.

According to the second embodiment and the modified examples thereof,the shaft 26 and the hub-side encircling member 108 are separate parts.However, depending on an application, it is desirable to further improvethe strength of the shaft, and integrated configuration of the shaft 26and the hub-side encircling member 108 is possible in this case.

When such a configuration is employed, the strength further increases byintegration. Moreover, the number of assembling processes can bereduced, and the leak-out of the lubricant from a fitted part of theshaft 26 and the hub-side encircling member 108 can be suppressed.

Moreover, according to such a configuration, in comparison with themodified example shown in FIG. 10, the precision of the outer diameterof the shaft can be easily accomplished by grinding.

According to the second embodiment and the modified examples thereof,the explanation was given of the case in which the external-sideencircling member 106 is fixed to the inner periphery of the outercylinder 103, but the present invention is not limited to thisconfiguration. The external-side encircling member 106 may be fixed to,for example, the hub 28.

According to the second embodiment and the modified examples thereof,the explanation was given of the case in which the rotating-body-sideencircling member 105 is formed by separately forming the inner cylinder1051 and the outer cylinder 1052 and then joining those pieces together.However, the present invention is not limited to this configuration. Forexample, the inner cylinder 1051 and the outer cylinder 1052 may beintegrally formed from the start.

According to the second embodiment and the modified examples thereof,although the explanation was given of the case in which the hub 28 andthe rotating-body-side encircling member 105 are joined together, thepresent invention is not limited to this configuration. For example, thehub 28 and the rotating-body-side encircling member 105 may beintegrally formed from the start. In this case, an outer periphery 28 gof the hub 28 and the inner periphery 1051 a may be successively cut andmachined. This easily suppresses inconsistency of the center of theouter periphery 28 g of the hub 28 and the center of the inner periphery1051 a of the rotating-body-side encircling member 105.

According to the first and second embodiments and modified examplesthereof, although the explanation was given of the so-called outer rotortype having the cylindrical magnet 32 located outwardly of the stackedcore 40, the present invention is not limited to this type. For example,the present invention can be applied to a so-called inner rotor typehaving a cylindrical magnet located inwardly of a stacked core.

Although the explanation was given of the case in which the stacked coreis used in the first and second embodiments and the modified examplesthereof, the core may be other than the stacked core.

What is claimed is:
 1. A rotating device comprising: a fixed body including a base formed with a through-hole, a base-side encircling member fixed to the through-hole, and a shaft fixed to the base-side encircling member; and a rotating body including a rotating-body-side encircling member that encircles the shaft, and a hub which is fixed to the rotating-body-side encircling member and on which a recording disk is to be mounted, wherein: a first dynamic pressure generating groove is formed in either one of an inner periphery of the rotating-body-side encircling member and an outer periphery of the shaft, and a second dynamic pressure generating groove is formed in either one of the inner periphery of the rotating-body-side encircling member and the outer periphery of the shaft at a location which is distant from the first dynamic pressure generating groove in an axial direction and which is an opposite side to the base-side encircling member; a first capillary seal portion and a second capillary seal portion are provided in a gap between the fixed body and the rotating body, and a path of a lubricant is present therebetween from the first capillary seal portion, the first dynamic pressure generating groove, the second dynamic pressure generating groove, and the second capillary seal portion in this order; the base-side encircling member comprises a cylinder part encircling a part of the rotating-body-side encircling member; and the first capillary seal portion is provided on an outer periphery of the cylinder part.
 2. The rotating device according to claim 1, wherein the first capillary seal portion is located between the first dynamic pressure generating groove and the second dynamic pressure generating groove in the axial direction.
 3. The rotating device according to claim 1, wherein: a part of the shaft at the base side is fixed to the base-side encircling member by interference fitting; and the base-side encircling member is fitted in and bonded and fixed to the through-hole of the base.
 4. The rotating device according to claim 1, further comprising an external-side encircling member which encircles the cylinder part and which is fixed to the hub, wherein the first capillary seal portion is provided between an inner periphery of the external-side encircling member and the outer periphery of the cylinder part.
 5. The rotating device according to claim 4, wherein: the base includes a protrusion that protrudes from a surface of the base at the hub side so as to encircle the external-side encircling member; and the protrusion and the external-side encircling member form a labyrinth seal.
 6. The rotating device according to claim 5, wherein a width of the labyrinth seal in a radial direction is equal to or smaller than ⅕ of a length of the labyrinth seal in the axial direction.
 7. The rotating device according to claim 5, wherein: a core including an annular part and a salient pole extending outwardly in the radial direction from the annular part is fixed to an outer periphery of the protrusion; and a magnet facing the salient pole in the radial direction is fixed to the hub.
 8. The rotating device according to claim 1, wherein a third dynamic pressure generating groove is formed in either one of an end face of the cylinder part and a surface of the rotating body facing with the end face in the axial direction.
 9. The rotating device according to claim 1, wherein: the fixed body includes a hub-side encircling member which encircles a portion of the shaft at the hub side and which is fixed to the shaft; and the second capillary seal portion is located between the hub-side encircling member and the rotating body.
 10. The rotating device according to claim 9, wherein a fourth dynamic pressure generating groove is formed in either one of a surface of the rotating-body-side encircling member and a surface of the hub-side encircling member, which surfaces face with each other in the axial direction.
 11. The rotating device according to claim 9, wherein a cap that covers the second capillary seal portion and a part of the hub-side encircling member is fixed to the rotating body.
 12. The rotating device according to claim 1, wherein: the shaft includes a shaft periphery that is a side face decreasing a diameter toward an opposite side to the base in the axial direction; the rotating-body-side encircling member includes a second inner periphery that is a side face encircling the shaft periphery and decreasing a diameter toward the opposite side to the base in the axial direction; and the second capillary seal portion is provided between the shaft periphery and the second inner periphery.
 13. The rotating device according to claim 1, wherein the rotating body includes a pathway that causes the first capillary seal portion and the second capillary seal portion to be linearly in communication with each other.
 14. A rotating device comprising: a fixed body including a base formed with a through-hole, a base-side encircling member fixed to the through-hole, and a shaft fixed to the base-side encircling member; and a rotating body including a rotating-body-side encircling member that encircles the shaft, and a hub which is fixed to the rotating-body-side encircling member and on which a recording disk is to be mounted, wherein: a first dynamic pressure generating groove is formed in either one of an inner periphery of the rotating-body-side encircling member and an outer periphery of the shaft, and a second dynamic pressure generating groove is formed in either one of the inner periphery of the rotating-body-side encircling member and the outer periphery of the shaft at a location which is distant from the first dynamic pressure generating groove in an axial direction and which is an opposite side to the base-side encircling member; a first capillary seal portion and a second capillary seal portion are provided in a gap between the fixed body and the rotating body, and a path of a lubricant is present therebetween from the first capillary seal portion, the first dynamic pressure generating groove, the second dynamic pressure generating groove, and the second capillary seal portion in this order; the base-side encircling member comprises a cylinder part encircling a part of the rotating-body-side encircling member; the fixed body includes a hub-side encircling member which encircles a portion of the shaft at the hub side and which is fixed to the shaft; the first capillary seal portion is provided on an outer periphery of the cylinder part; and the second capillary seal portion is located between the hub-side encircling member and the rotating body.
 15. The rotating device according to claim 14, wherein the first capillary seal portion is located between the first dynamic pressure generating groove and the second dynamic pressure generating groove in the axial direction.
 16. The rotating device according to claim 14, further comprising an external-side encircling member which encircles the cylinder part and which is fixed to the hub, wherein the first capillary seal portion is provided between an inner periphery of the external-side encircling member and the outer periphery of the cylinder part.
 17. The rotating device according to claim 16, wherein: the base includes a protrusion that protrudes from a surface of the base at the hub side so as to encircle the external-side encircling member; and the protrusion and the external-side encircling member form a labyrinth seal.
 18. The rotating device according to claim 17, wherein a width of the labyrinth seal in a radial direction is equal to or smaller than ⅕ of a length of the labyrinth seal in the axial direction.
 19. The rotating device according to claim 14, wherein a third dynamic pressure generating groove is formed in either one of an end face of the cylinder part and a surface of the rotating body facing with the end face in the axial direction.
 20. The rotating device according to claim 14, wherein the rotating body includes a pathway that causes the first capillary seal portion and the second capillary seal portion to be linearly in communication with each other. 